Fish oil study: Fish oil might increase prostate-cancer risk, Men who take fish-oil supplements or eat a lot of fatty fish expecting health benefits might actually increase their risk for prostate cancer, including aggressive types that are harder to treat.That news comes out of a study published online yesterday in the Journal of the National Cancer Institute and follows an analysis last year of 20 fish-oil studies that concluded that supplements offer no clear heart benefits.

The authors of the study, the second they’ve done that found an association, say men would be well-served to skip supplements. Other experts say the new study is provocative but not definitive because the relationship between fatty acids and cancer is not well understood.

Americans spend about $1 billion a year on fish-oil supplements.

The study looked at 2,227 men, 834 of whom had prostate cancer. Of the cancer patients, 156 had high-grade, or more aggressive, cancer.

Men with higher levels of long-chain fatty acids in their bloodstream had a 43 percent increased risk for prostate cancer compared with those with lower levels.

And they had a 71 percent increased risk of more aggressive cancers, according to a statistical analysis by researchers including cancer epidemiologist Theodore Brasky, who now works at Ohio State University’s Comprehensive Cancer Center.He worked on the project at Seattle’s Fred Hutchinson Cancer Research Center.

Of the 176 men with prostate cancer who had the lowest fatty-acid levels, 26 had more-serious cases. Of the 245 with the highest levels, 43 had high-grade cancer.

Brasky’s co-author, Alan Kristal, an epidemiologist in Seattle, pointed to several studies debunking theories that vitamins and minerals ward off cancer and other disease.

“Why would you do it? Americans have been sold a complete bill of goods on supplements,” he said. “I think the message increasingly is that these are not good for you.”The new study offers no recommendations on how much omega-3 fatty acid is reasonable, nor did the researchers recommend that men stop eating fish.

With their first study, “We made everyone a little nervous. The findings were opposite from what we expected initially,” Brasky said.